Liquid crystal door window shutter arrangement for self-cleaning cooking oven

• US 3,898,977 A
• Filed: 01/28/1974
• Issued: 08/12/1975
• Est. Priority Date: 01/28/1974
• Status: Expired due to Term

• Current Assignee: Robert Draper
• Original Assignee: Robert Draper
• Inventors: Draper, Robert
• Primary Examiner(s): Dority, Jr., Carroll B.
• Assistant Examiner(s): Schwartz, Larry I.
• Application Number:
  US05/437,433
• Time in Patent Office: 561 Days
• Field of Search: 126/200,197 350/16LC
• US Class Current: 126/200
• CPC Class Codes: F24C 15/04 with transparent panels

Abstract

A pyrolytic self-cleaning oven door is provided having a window comprising a liquid crystal material, disposed between an inner surface and an outer surface of the window. The liquid crystal serves as an optical shutter. The shutter arrangement affects a change in light transmission therethrough in accordance with the temperature in the oven. The shutter is in a substantially opaque state when the oven is at a pyrolytic self-cleaning temperature and in a substantially transparent state, when the oven is at a temperature below a pyrolytic self-cleaning range.

Claims

1. In a pyrolytic self-cleaning cooking oven, said oven having an opening thereinto;

a door for closing said opening, said door having a window therein;

means including a liquid crystal material associated with said window for providing an optical shutter operative at elevated temperatures in said oven corresponding to a heat-cleaning temperature range; and

said means permitting transmission of light sufficient for viewing through said window when the temperature of said oven is below the heat cleaning range and excluding transmission of light sufficient for viewing through said window when the temperature of said oven is in a heat-cleaning range.

2. In the oven of claim 1 wherein:

said liquid crystal material comprises a cholesteric liquid crystal; and

said means includes two mutually opposed linearly polarizing light filters with the polarity of each being generally perpendicular with respect to the other, and wherein said liquid crystal material is disposed therebetween.

3. In the oven of claim 2 wherein:

said liquid crystal material is of a character that it responds to temperatures transmitted to it during normal cooking in said oven to rotate light passing therethrough; and

to temperatures transmitted to it during pyrolytic cleaning operations of said oven, to provide substantially negligible rotation of said light therethrough.

4. In the oven of claim 1 wherein:

said liquid crystal material comprises a nematic liquid crystal material confined between spaced apart electrode layers.

5. In the oven of claim 4 wherein:

said means for providing an optical shutter further includes;

a circuit having a voltage source for serially cOnnecting said layers of said conducting material with said nematic liquid crystal material and switch means for completing said circuit, and means for moving said switch means to a closed position in response to said oven being in a heat-cleaning operation whereby said liquid crystal transforms into a turbid state preventing transmission of sufficient light for viewing therethrough.

6. In the oven of claim 5 wherein:

said voltage source comprises a thermopile, a portion of which is substantially exposed to the elevated temperature of said oven to generate said voltage means.

7. In an improved open door for a pyrolytic self-cleaning oven having a window for normally viewing the interior of an oven and means for obstructing viewing therethrough during a heat-cleaning cycle and wherein the improvement comprises:

said means for obstructing viewing includes a pair of opposed parallel spaced panes associated with said window and said space between said panes contains a conditionally responsive liquid crystal material of a character that responds to said oven being at heat-cleaning temperatures to alter the transmission of light through said panes in a manner to prevent viewing through said window.